LASER INDUCED OPTICAL PUMPING

Author

GIBERSON, KARL WILLARD

Date

1985

Degree

Doctor of Philosophy

Abstract

Optical pumping is a very useful technique for the production of spin polarized particles. This thesis describes laser induced optical pumping in helium, argon, and neon metastable atoms. The laser used to optically pump helium is an (F(,2)+)* color center laser which was developed during the course of this work. Argon and neon were optically pumped with commercially available dye lasers.
In the first experiment the color center laser was used to spin polarize a Doppler broadened ensemble of He 2('3)S metastable atoms contained in a flowing helium afterglow. The extracted chemi-ionized electron polarization was as high as 80%, indicating almost complete polarization of the 2('3)S atoms. A P('2)I quality factor of 8 x 10('-6) was obtained.
The next set of experiments involved the optical pumping of metastable atoms contained in collimated beams. Although substantial polarizations were achieved, problems were encountered with laser frequency jitter as none of the lasers were frequency stabilized. In particular, the polarizations obtained in both helium and argon were unstable and not even a nominal polarization could be maintained consistently over any reasonable time interval. Stable optical pumping in neon was obtained with the DCM dye laser however, due to frequency jitter which essentially broadened the narrow spectral components in the laser lineshape.
In an effort to improve on the limited performance obtained in the optical pumping of both helium and argon, a frequency modulation technique has been developed. By decomposing the very narrow spectral components present in typical laser radiation into a large number of closely spaced sidebands, this technique effectively fills in the gaps in the laser linewidth. This broad continuous linewidth enhances the ability of unstabilized lasers to optically pump very narrow atomic transitions by reducing the effects of laser detuning. In an initial experiment almost complete polarization of a beam of argon metastable atoms was obtained using a frequency modulated LD 700 dye laser. The polarization was stable on a time scale of several hours--more than adequate for proposed spin dependent studies.